The overall goal of the proposed studies is to continue to develop, validate and disseminate effective treatments for the understudied population of adult marijuana abusers. Included within this goal are the identification of individual and situational characteristics that predict success with particular interventions and a test of the efficacy of outreach and re-treatment efforts for previously treated subjects who have relapsed. Study 1 will examine the long-term thirty month post- treatment outcomes for subjects who received either a Relapse Prevention (RP) or Social Support (SS) oriented group treatment for chronic marijuana abuse. These data will provide important information on a) the long-range stability of abstinence outcomes generated by these treatments, b) the subsequent treatment-seeking behavior of subjects not abstinent at the twelve-month follow-up, c) the rates of unaided and assisted quitting for non-abstinent subjects at the twelve-month follow- up, and d) the pre- and post-treatment demographic and psychosocial variables related to long-term success in modifying marijuana use. Study 2 will recruit a new sample of adult marijuana abusers and compare the effectiveness of a modified relapse prevention group intervention with a minimal intervention. The relapse prevention support group (RPSG) will deliver the relapse prevention content in the context of a support group, extend the treatment period, involve partners in a concurrent relapse prevention group, and build self-sustaining support groups. In contrast, the minimal intervention will rely on individualized assessment and advice (IAA) given by an expert. The tow approaches represent opposite ends of a continuum of professional and client involvement in treatment. A delayed treatment control group (DTC) will provide a basic for evaluating outcomes of the active treatments. This randomized, three- group (RPSG, IAA, DTC) clinical experiment will produce outcome data for sixteen months after the start of treatment and provide data on a) the relative efficacy of minimal versus maximal approaches to treating marijuana abuse, b) the increments inabstinence rates produced by active treatments above the base rate identified in the DTC group, and c) the identification of subject characteristics and psychosocial variables predictive of treatment completion and marijuana cessation with each type of treatment. Study 2 will also attempt to re-treat nonabstinent subjects from the currently funded study in order to determine the efficacy of such outreach efforts to unsuccessful clients.